Ovulation introduction .
[1]. Ovulation is the process by which the graafian follicle in the ovary ruptures and the ovum is released into the abdominal cavity.
[2]. Ovulation occurs on the 14th day of menstrual cycle in a normal cycle of 28 days. The ovum, which is released into the abdominal cavity, enters the fallopian tube through the fimbriated end of the tube.
[3]. Usually, only one ovum is released from any one of the ovaries. LH is responsible for ovulation.
Process of Ovulation .
Prior to ovulation, large amount of LH is secreted (luteal surge). This causes changes in the graafian follicle leading to ovulation.
Stages of Ovulation.
1. Graafian follicle moves towards the periphery of ovary.
2. New blood vessels are formed in the ovary by actions of LH and progesterone.
3. These blood vessels protrude into the wall of the follicle.
4. This increases the blood flow to the follicle.
5. Now, prostaglandin is released from granulosa cells of the follicle.
6. It causes leakage of plasma into the follicle.
7. Just before ovulation the follicle swells and protrudes against the capsule of the ovary. This
protrusion is called stigma.
8. Then, progesterone activates the proteolytic enzymes present in the cells of theca interna.
9. These enzymes weaken the follicular capsule and cause degeneration of the stigma.
10. After about 30 minutes, fluid begins to ooze from the follicle through the stigma.
11. It decreases the size of the follicle causing rupture of stigma.
12. Now, ovum is released from the follicle along with fluid and plenty of small granulosa cells into the abdominal cavity.
Determination of Ovulation Time.
Various methods are available to determine the ovulation time. In human beings, usually indirect methods are adopted such as:
1. Determination of basal body temperature.
2. Determination of hormonal excretion in urine.
3. Determination of hormonal level in plasma.
4. Ultrasound scanning.
5. Cervical mucus pattern.
Determination of Basal Body Temperature.
[1]. Body temperature is measured for few days during the mid period of menstrual cycle. Temperature is measured in the morning by placing the thermometer in rectum or vagina.
[2]. There is a slight fall in the basal temperature just prior to ovulation. And the temperature increases after ovulation. The alteration in the temperature is very mild and it is about ± 0.3°C to 0.5°C.
[3]. The increase in temperature is due to the thermogenic effect of progesterone.
Determination of Hormonal Excretion in Urine.
[1]. At the time of ovulation, there is an increase in the urinary excretion of metabolic end products of estrogen and progesterone.
[2]. The end products of estrogen metabolism are estrone, estriol and 17-β-estradiol. The end product of progesterone metabolism is pregnanediol.
Determination of Hormonal level in Plasma.
[1]. Plasma level of FSH, LH, estrogen and progesterone is measured.
[2]. Hormone level is altered at the time of ovulation and after ovulation.
At the time of ovulation:
1. FSH level decreases.
2. LH level increases.
3. Estrogen level increases.
After ovulation:
Progesterone level increases.
Ultrasound Scanning.
Process of ovulation can be observed in ultrasound scanning.
Cervical Mucus Pattern.
[1]. When the cervical mucus spread on a slide is examined under microscope, it shows a fern pattern.
[2]. This pattern disappears after ovulation.
Significance of Determining Ovulation Time.
Determination of ovulation time is helpful for family planning by Rhythm method .
Rhythm Method (Safe Period).
[1]. Rhythm method of fertility control is based on the time of ovulation.
[2]. After ovulation, i.e. on the 14th day of menstrual cycle, the ovum is fertilized during its passage through fallopian tubes.
[3]. Its viability is only for 2 days after ovulation and should be fertilized within this period.
[4]. Sperms survive only for about 24 to 48 hours after ejaculation in the female genital tract.
[5]. If sexual intercourse occurs during this period, i.e. between few days before and few days after ovulation, there is chance of pregnancy. This period is called the dangerous period.
[6]. Pregnancy can be avoided if there is no sexual intercourse during this period. The prevention
of pregnancy by avoiding sexual mating during this period is called rhythm method.
[7]. The periods, when pregnancy does not occur are 4 to 5 days after menstrual bleeding and 5 to 6 days before the onset of next cycle. These periods are together called safe period.
Advantages and Disadvantages of Rhythm Period.
[1]. It is one of the most successful methods of fertility control provided the woman knows the exact day of ovulation. However, it is not a successful method because of various reasons.
[2]. Basic knowledge about the menstrual cycle is necessary to determine the day of ovulation.
[3]. Self-restraint is essential to avoid sexual intercourse. Because of the practical difficulties, this method is not popular.
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